1. Field of the Invention
The invention relates to a roof drainage device, and more particularly to a rainwater head.
2. Description of the Related Art
A typical rainwater head includes a dome and a drainage pipe connected to the lower part of the dome. An opening is arranged on the top of the drainage pipe and functions as a drainage exit. When assembling the rainwater head, the drainage exit is disposed on a low-laying area that is relatively lower than the roof for draining the accumulated water out of the roof as soon as possible. However, with the enlargement of areas impervious to water, such as concrete constructions, asphalt pavements, and parking lots, water flow and the peak flow on the ground surface of the city increase in case of cloudbursts, which results more and more serious problems of urban waterlogging. Disadvantages of the present rainwater heads lie in that neither the drainage of the rainwater is prolonged nor the peak flow of the rainwater is reduced, so that urban waterloggings easily occur in case of frequent and heavy rainfalls.